The use of towable vehicles has become increasingly popular for both utilitarian and pleasure purposes. A wide variety of both tractor and trailer vehicles are employed for general or special purposes. Tractor vehicles, for example, include both those that travel on road, such as cars, sport utility vehicles, trucks, semi-tractors and a wide variety of farm and agricultural tractor equipment. Trailer vehicles, on the other hand, include utility trailers, commercial trailers, recreational vehicle trailers, boat trailers, camping trailers, to name a few.
One of the most common structures used to link a tractor vehicle to a trailer vehicle is the hitch ball and trailer coupler. Here, a mounting structure is provided on the tractor vehicle, and the mounting structure supports a generally spherical hitch ball in an upright manner. The trailer vehicle then includes a tongue associated with the frame of the trailer vehicle with this tongue having a forwardly extending hitch ball coupler that includes a recess that mateably receives the hitch ball and that can be secured thereto during the towing operation. During the towing operation, the hitch ball and the trailer hitch coupler are latched together to prevent inadvertent disengagement. In addition, it is known to provide the latch mechanisms of the trailer hitch coupler with a locking device so that the trailer can be locked onto the hitch ball.
However, when a trailer vehicle is disconnected from the towing vehicle, it may become the target of unauthorized use or theft. In such cases, a thief or other user may merely attach another towing vehicle to the trailer hitch coupler and drives away with the trailer vehicle. In order to deter theft, it is known to lock the trailer hitch coupler latch in an unlatched condition so that it may not be secured in a normal manner to another tractor vehicle. However, the recess of the trailer hitch coupler is still available for mating with a hitch ball of a thief's tractor vehicle.
Accordingly, it is also known to provide a locking structure that engages the hitch ball recess of a trailer hitch coupler and locks onto the trailer hitch coupler so that the locking device interferes with the ability to attach a tractor vehicle. For example, U.S. Pat. No. 5,433,468 issued Jul. 8, 1995 to Dickson discloses a theft resistant device wherein a cylindrical member may be inserted into the recess of a trailer hitch coupler. A pair of arms are pivotally secured to this cylindrical member, on either side thereof, so that they may pivot across the top of the trailer hitch coupler and be secured by a lock shackle that may pass through openings in the free ends of the arms. This device, however, can be subject to attack by a thief and removed simply by hammering the arms out of alignment or breaking the arms off of the device so that the cylinder, and thus the locking device, may be removed from the trailer hitch coupler.
In U.S. Pat. No. 4,141,569, issued Feb. 27, 1979 to Dilk, another theft prevention device for use on a detached trailer vehicle is disclosed. Here, a hitch ball structure is mounted in a box-like housing that has a hinged lid. The hitch ball structure is positioned in the recess of a trailer hitch coupler, and the lid is then pivoted into place so as to trap the hitch coupler between the hitch ball structure and a downwardly depending post that is mounted to the lid. The lid may then be padlocked into a closed position. U.S. Pat. No. 4,032,171, issued Jun. 28, 1977 to Allen et al., teaches a somewhat similar technique of locking a trailer hitch coupler. Each of these devices are relatively bulky and complex and again are subject to attack by a thief due to the exposed parts.
U.S. Pat. No. 3,884,055, issued May 20, 1975 to Vuillemot also locks into the recess of a trailer hitch coupler. Here, a cylindrical post is mounted to a U-shaped bracket with the post sized to be received in the recess. The legs of the bracket are provided with openings through which a bar that extends across the trailer hitch coupler and the post with this bar being locked in the bracket by means of a padlock. While this device is rather compact, it still exposes the locking structure to attack by a thief.
While the above-referenced devices do, in fact, lock onto a trailer hitch coupler, they suffer other disadvantages in addition to those noted above. For example, none of the devices disclosed in the above-referenced patents are readily adjustable for differently dimensioned trailer hitch couplers moreover, each relies on an independent padlock which can inadvertently be misplaced so that the locking structure becomes less useable until another padlock is obtained.
Accordingly, there remains a need for improved locks which may lock onto a trailer hitch coupler in order to discourage theft of a trailer vehicle when it is detached from a towing vehicle. There is a need for a device which is both compact, strong and durable such that the device resists attack by a would-be thief. There is further a need for such a locking device that has a locking mechanism incorporated therein so as to avoid the requirement of an auxiliary padlock.